Spatial Reference Manual
Page 50 of 158
Version 4.4
04/06/2019
navigation initialisation is an external position source, see section 12.2 for more
information. In a situation where a GNSS fix is not available to initialise navigation, it
can be initialised manually by entering a position into the position dialogue in Spatial
Manager, see section 11.8.12. Once navigation initialisation is complete, the position,
velocity and acceleration values will be valid.
10.1.3
Heading Initialisation
Heading initialisation completes once the system has determined a heading. The
conditions required to determine a heading depend upon the heading source being
used, see section 10.4. If magnetic heading is enabled as a heading source the
heading initialisation should complete within 2 seconds after power on. If magnetic
heading is disabled and velocity heading is used as the only heading source, the
heading will initialise once the system travels at a speed of over 1.15 metres/second
for over 5 seconds with a 3D GNSS fix. If the system is hot starting it will remember its
heading from when it was switched off and use this as the starting heading until
another source becomes available.
Until the heading has been initialised, the system will not be able to navigate without
a GNSS fix and the roll and pitch values will not be able to reach full accuracy.
10.1.4
Time Initialisation
Time initialisation completes once the system has determined time to an accuracy of
less than 1 microsecond. This normally occurs as soon as the GNSS receiver obtains its
first fix. It is also possible to provide an external source of time, see section 12.2 for
more information on external time sources.
Until the time has initialised the values of Unix time and formatted time that Spatial
outputs will not be valid and may change.
10.2 Hot Start
Spatial is the first GNSS/INS on the market with hot start functionality. This allows
Spatial to start inertial navigation within 500 milliseconds and obtain a GNSS fix in as
little as 3 seconds. Spatial's hot start is always on and fully automatic.
A next generation backup battery system within Spatial provides the hot start ability
for more than 48 hours without power. When Spatial hot starts it assumes that it is in
the same state it was when it lost power and begins navigating from that position. The
hot start also provides ephemeris, almanac and time information to the GNSS receiver
which allows it to achieve a fix far more quickly than it otherwise would. When the
GNSS achieves its first fix, if this position deviates from the hot start position, Spatial
will jump to the new position without causing any side effects to the filter.
Whilst Spatial is without power it keeps track of the time accurately to within 1 second
so that the time is immediately valid on a hot start.
Spatial's hot start is of particular benefit to vehicle tracking and robotics applications.
The primary benefits are immunity and fast recovery from power failure as well as fast
startup time.
